This invention relates to a non-rotary tool for injecting a fluid fertilizer composition, such as anhydrous ammonia, into a furrow in the ground. More particularly, this invention relates to a fertilizer knife for preparing a furrow in the ground and for directing the fertilizer into the furrow below ground level.
The application of liquid fertilizer over the surface of the ground has been known for many years, but has been found to be unsatisfactory because the fertilizer penetrates the surface of the soil relatively slowly resulting in part of the fertilizer evaporating before it is taken up by the soil. Subsequent rainfall washes much of the remaining fertilizer away. To overcome these problems, deep placement of liquid fertilizer has been carried out and has been found to be beneficial to plant growth.
Earth penetrating tools and applicator blades have been devised for distributing liquid fertilizer in a desired pattern at various depths below the surface of the soil. Fertilizer distributors of this type have one or more cultivator blades that are drawn through the soil by a tractor. Each blade is provided with a tube extending down the rearward edge for conducting the liquid fertilizer to the lower end of the blade for injection in the soil. The blades are usually provided with a supporting shank secured to a lift-type cultivator drawbar.
Liquid anhydrous ammonia injected into the ground is normally maintained under pressure, and the ammonia reverts to a vapor state upon release of the pressure during application. Conversion of the liquid anhydrous ammonia into a vapor usually occurs very readily during the time of year when the fertilizer is applied--namely, during fairly warm weather. Since the anhydrous ammonia may escape from the furrow before being absorbed into the ground, the applicator blade must be designed so that the loss of fertilizer through vaporization is minimized.
Certain portions of the fertilizer applicator blade wear very rapidly while the main body of the blade remains in good condition. For example, the fertilizer knife has a leading edge that opens the furrow in the soil. This edge is subject to great wear and early failure caused by the abrading action of the soil and by impact with objects, such as roots and stones. Early failure of the fertilizer tube on the rear of the blade may also occur because the tube usually has relatively thin side walls that are subject to soil abrasion. Thus, the design of the applicator blade should be such that accelerated wear on portions of the blade is minimized.
Moreover, it is well understood by workers in the field that even a fertilizer applicator blade of the best design will wear and must eventually be reconditioned. In these circumstances it is important that the earth-engaging and contacting surfaces be capable of being easily removed and replaced or restored with a minimum of effort and expense.
There exists a need in the art for a fertilizer applicator knife capable of fulfilling the requirements of use with fluid fertilizers, such as anhydrous ammonia. The fertilizer knife should be designed to ensure absorption of the anhydrous ammonia in the soil without the escape of vapor from the furrow. The fertilizer knife should also be resistant to wear on all its operating surfaces and be capable of being reconditioned quickly and easily by removing and replacing or restoring worn surfaces.